Gum inhibitors for gasoline



PRECIPITATMN TEMPERATURE-DEREE FAHRENHf/T F mm 9 LE CAL ULATED Q k E 09I 3.

Oct. 13, 1959 M. R. BRIMER 2,908,558

cum INHIBITORS FOR GASOLINE Filed Feb. 3, 1955 PERCENT D/ ALKYLA TEDINHIBHUR 20 3O 4O 5O 6O 7O PERCENT DI ALKYLATED INHIBITOR [N BLEND INVENTOR.

ATTORNEYS MarsbaIIRBI-imer stocks are normally subject to gum.formation,

United States Patent GUM INHIBITORS FOR GASOLINE Application February 3,1955, Serial" No. 486,001

Claims. (Cl. 44]'-'l5) This invention relates to synergistic guminhibitors for gasoline and to stabilized gasoline compositions.

Motor fuels and particularly gasolines, containing a substantial amountof thermally or catalytically crac%gd e N-monoalkyl-p-aminophenolsareused widely for effectively obviating objectionable gum formation,usually admixed with about 10% by weight of N,N'-dialkyl-pphenylenediarnine, and such inhibitors are commonly added' to the gasoline as asolution in'a suitable organic solvent such as an alcoholor-the like.' i

It is an object of this invention to provide improved gum inhibitorscomprising a mixture of components exhibiting synergistic inhibitoractivity,

It is a further object of this invention to stabilize gasoline with anew and improved synergistic inhibitor composition, and particularlywitha synergistic inhibitor composition, having unusual solubilityproperties and av much lower precipitation temperature than would beexpected from the individual components thereof.

Another object of the invention is to provide mixtures of anN-monoalkyl-p-aminophenol and an N,N-diallrylp-aminophenol which exhibitgum inhibiting potencies higher than would be expected from thepotencies of the individual components of the mixture, and particularlyto provide such mixtures containing a substantial amount of anN,N'-dialkyl-p-phenylene diamine.

2,908,558 Patented Oct. 13, 1959 ice 2.: sirably contain a substantialamount, i.e. 5-20%, and preferably about 10% by weight ofN,N'-dialkyl-pphenylene diamine basedon the weight of theN-monoalkyl-p-aminophen'ol.

The improved results obtained with the preferred compositions embodyingthe invention are illustrated in the drawings.

Fig .1 illustrates the synergistic effect in gasoline observed withmixtures, of N'-n-butyl-p-aminophenol and N-n-butyl-N-isobutylp-aminophenol, containing 10% of N,N-di-n-butyl-p-phenylene diaminebased onthe weight of the N-n-butyl-p-aminophenol, as contrasted withthe calculated activity to. be expected from the activity of theindividual components over the entire range from 0% to 100% of each ofthe monoalkyl' and the dialkyl aminophenols. The inhibitor ratio is theratio of the inhibitor activity of the new mixture to the inhibitoractivity, taken as 1.0, of a mixture of 90% by weight ofN-n-butyl-p-aminophenol and 10% by weight of N,N'-di-n-butyl-p-phenylenediamine.

Fig. 2 illustrates the improved precipitation temperature obtained withthe mixtures. of Fig. l at a. 20%

. level in straight run gasoline, the composition at.0%

Another object of the invention is to provide improved gum inhibitorcompositions whereby the inhibitor can be used in lower amounts than waspossible with the N-monoalkyl-p-aminophenols alone to give a desiredinhibiting action, or conversely whereby an equal level of the improvedinhibitor of this inventionwill give a higher level of inhibiting actionthan will the prevously employed N-monoalkyl-p-aminophenol.

. Other objects of the invention will be apparent from the descriptionand claims which follow.

' These and other objects, are attained by means of this invention asdescribed more fully hereinafter and illustrated in the drawings and asd fined in the appended claims. I have found that mixtures of anN-monoalkylp-aminophenol and an N,N-dialkyl-p-aminophenol exhibit asynergistic inhibiting efiect, on gum formation in motor fuels which issubstantially higher than to be expected from the inhibiting action ofthe components considered individually. This synergistic efiect'isapparent with the various combinations of N -m onoalkyl p-aminophenolsand N,N-dialkyl aminophenols wherein the various alkyl groups containl6.carbon atoms. The alkyl groups can 'be the same or difierent alkylgroups as defined; and, as described hereinafter, particularly goodresults are obtained when the alkyl groups in the dialkylated materialdiftereither in number of carbon atoms or structural co nfig uration orboth; Particularly advantageous results are obtained with mixtures ofN-n-butyl-p-aminophenol and N-n-butyl-N-isobutylp-ami-nophenol. From thestandpoint of solubility and dialkylated inhibitor consisting of amixture of 90% by weight of N-n-butyl-p-aminophenol and 10% by weight ofN,N'-din-butyl p-aminophenol.

As can be seen from Fig. l, the synergism is. apparent over the entirerange of concentrations; Because of the lower individualpotency of thedialkylated inhibitor, however, the. activity of the blend is lower thanthat of the monoalkylated inhibitor in the range of 90-l0,0% of thedialkylated inhibitor even with the synergistic action. Consequently,the. preferredcompositions comprise a. mixture.- of 1-90,-% by weight ofN-n-butyl-N- isobutyl-p-aminophenol. and 99-10% by weight; ofN-nbutyl-p-aminophenol, with the optimum activity in the range about20-50% of dialkylated inhibitor and 80- 50% of monoalkylated' inhibitor.The compositions desirably employed are those in the range of 2535% byweight of N-n-butyl-N-isobutyl-p-aminophenol and 75- 65% by weight ofN-HrbHtYI-PPEIIHI HOPheHOI with or without about 10% by weight ofN,N'-di n bl.ltyl-pphenylene diamine; based on the weight ofN-n-butyl-paminophenol. 'j f f Similar mixtures ofN-n-butyl-p-aminophenol; and N,N-di-n-butyl-p-aminophenol also showsynergism over the entire range of proportions, but the inhibitor ratiodrops below 1.0 at" about 65% concentrationof-the dialkyl component, andhence this blend is less desirable. Furthermore, the preparation 'of'the N-n-butyl-N-iso butyl-p-aminophenol is preferred because of economicreasons, and, in the preferred catalytic process, catalyst poisoning isreduced. A

The N,N-dialkyl'-p-aminophenols can be prepared by any desired method.In one process, p-nitrophenol can be reacted with an alkyl aldehyde inthe presence of hydrogen and a hydrogenation catalyst, in an organicsolvent whichis preferably the alcohol corresponding to the aldehydeemployed. In this case, the alkyl groups in the mixture of monoalkylatedinhibitor and dialkylated inhibitor obtained are the same. This methodof preparation is illustrated by the following examples.

. EXAMPLE 1;

A mixture of 70.0 g. (0.5 mole) ofp-nitrophenol, 10.0 g. of Raney nickeland 159.3 g. (2.16 moles) of n-butanol was charged to an autoclave and620 psi, of hydrogen was applied. Theautoclave was warmed to 60-65 6,,

and a mixture. of 190.0 g. (2.64 moles) 'or' n-butyraldehyde and 12.9 g.(0.175 mole) of n-butanol wasted; in under pressure over a'3.5hour'period. The reaction-was continued for an additional 3.75" hours,and thereafter phenol and 74.4% which was essentiallyN-n-butyl-paminophenol. This product was separated into a causticsoluble fraction and a caustic insoluble fraction and the inhibitoractivity in Pennsylvania cracked gasoline at a 0.0048 weight percentconcentration of inhibitor was determined by the Active Oxygen Methodand compared with a standard inhibitor consisting of 90% by weight ofN-n-buty-l-paminophenol and 10% by weight of N,N- di-n-butyl-p-phenylenediamine. The inhibitor ratio was also calculated based on the inhibitorratio of the standard taken as 1.0.

From the inhibitor activities of the two fractions, the calculatedinhibitor ratio of the blend is only 0.97 whereas the actual inhibitorratio found experimentally was 1.07. This clearly demonstrates thesynergistic effect of the blend.

The elfecti've inhibitor action 'of the blends as compared toN-n-butyl-p-aminophenol when used at a 0.01% concentration in aPennsylvania blend of catalytic and thermally cracked gasoline is shownin Table 2.

Table 2 Effective Calculated Additive Inhibitor Inhibitor Ratio RatioN-n-butyl-p-aminophenol 1. N,N-di-n-butyl-p-aminophenol 0. 92 3 parts N-n-butyl-p-aminophenol 1 055 0 98 1 part N,N-di-n-butyl-p-aminophenol-85 parts N-n-butyl-p-aminophenol 0 99 0 95 65 parts N,N-di-n-butyl-p-arninophenol In the preferred process,N-monoalkyl-paminophenol, with or without N,N'-dialkyl-p-phenylenediamine, is re- .acted with an alkyl aldehyde inthe presence of hydrogenand a hydrogenation catalyst in an organic solvent. By this means, thealkyl groups in the dialkylated inhibitor can be the same or differentdepending upon the alkyl aldehyde employed. This process can be carriedonly partially to completion whereby a mixture of monoalkyl and dialkylinhibitor results, but it is often difiicultto control the amount ofalkylation to give the desired mixture. Consequently, it is preferred toconvert the N- monoalkyl-p-aminophenol completely to the. dialkylatedinhibitor and then blend this product with monoalkylated inhibitor tothe desired composition.

In this process as in the process illustrated in Example 1, Raney nickelis the preferred catalyst although other hydrogenation catalysts can besuccessfully employed such as supported nickel catalysts, platinum orpalladium catalysts, copper chromite catalysts and the like. The choiceof operating conditions depends largely on the catalyst employed. If thecatalyst employed is the preferred Raney nickel, the process can beoperated successfully over a temperature range of 25 C. to 120 C. and ahydrogen pressure range or 500 to 5000 p.s.i. The time required for theproces will, vary with the temperature example.

presence of hydrogenhand Raney nickel.

4 f and pressure; since an increase in either variable will decrease thetime required. In the process wherein monoalkyl-p-aminophenol isconverted, the preferred conditions are a temperature of 40 C. to C.with hydrogen pressure of 1000 p.s.i. to 2500 p.s.i. using a Raneynickel catalyst. Under these conditions, the process requires about 30minutes to 2 hours for completion when carried out batchwise in astandard rocking autoclave. If a supported nickel catalyst is used, alonger time is required and the operating temperature range is 100 C. toC. A copper chromite catalyst requirm an operating temperature range of125 C. to C. With platinum or palladium catalysts, the optimumtemperature range is 25-50 C. and a hydrogen pressure of 15-150 p.s.i.will suflice.

The process can be carried out in the absence of a solvent or in thepresence of a solvent. Usually it is desirable to use a solvent whichcorresponds to the byproduct of the reaction, i.e.methanol withformaldehyde,

ethyl alcohol with acetaldehyde, n-butanol with n-butyraldehyde,isobutyl alcohol with isobutyraldehyde, and the like. The advantageouscharacteristics of the preferred mixture of N-n-butyl-p-aminophenol andN-n-butyl-N- isobutyl-p-aminophenol are illustrated in the followingEXAMPLE 2 A mixture of 9 parts of N-n-butyl-p-aminophenol and one partof N,N-di-n-butyl-pphenylene diamine was alkylated with isobutyraldehydein isobutanol and in the The reaction mixture was filtered to remove thecatalyst. The low boiling components were removed by distillation andthe remaining crude base material was distilled at 2 mm. pressure. Theeffective inhibitor ratio of the resulting dialkylated product as wellas blends of the product with the original inhibitor mixture weredetermined by the Active Oxygen Method at a 0.01% concentration ofadditive in a Pennsylvania blend of thermal and catalytic crackedgasoline. The base in Table 3 designates a mixture of 9 parts ofN-n-butyl-p-aminophenol and 1 part of N,Ndi-n-butyl-p-phenylene diamine.

Table 3 Efiective Calculated Additive Inhibitor Inhibitor Ratio Ratio 1part Base 1. 068 0. 982

- The preferred blends as illustrated in Example 2 not concentrationrange as shown in Fig. 1, but they also have the advantage ofprecipitating from gasoline only at much lower temperatures than doesthe base mixture as shown in Fig. 2. Thus, as shown in Fig.2, when a 52%solution of inhibitor in isopropanol was added to straight run gasolineto give a 20% concentration of inhibitor, the precipitation temperaturedecreases rapidly from 1-45 F. for the base mixture of 9 parts ofN-nbutyl-p-a minophenol and 1 part of N,N-di-n-buty l-pphenylene-diaminedown to 50 F. when the blend consists of 40% of the base and 60% ofN-n-butyl-N- isobutyl-p-aminophenol.

- The synergism is also apparent with other blends of 'monoalkylated anddialkylated aminophenols. Of the' those cases, where one of the alkylgroups contains less than four-carbon atoms, the dialkylated inhibitoris often EXAMPLE 3 A mixture of 9 parts of N-n-butyl-phminophenol and 1part of N,N'-di-n-butyl-p-phenylene diamine (inhibitor base) wasalkylated with acetaldehyde in the presence of hydrogen and Raneynickel. The reaction mixture was purified as in the preceding exampleand the efiectiveness of the distilled dialkylated product consistingessentially Synergism is also apparent with blends containing N-methyl-N-n-butyl-p-aminophenol prepared by alkyla-tingN-n-butyl-p-aminophenol with formaldehyde in the presence of hydrogenand Raney nickel.

Table Efiective Calculated Additive Inhibitor Inhibitor Ratio RatioN-n-butyl-p-aminophenol 1. 00 N-methyl-N-n-buty1-p-arninophenol 1. 23 1part N-n-butyl-p-aminophenol 1 11 1 057 3 partsN-methyl-N-n-butyl-p-aminopheno1 In stabilizing motor fuels, theinhibitor blends of the invention can be used. in amounts of from 0.001%to 0.1% or as high as 1%, although concentrations of 0.005% to 0.05% areusually preferred. They can be used alone or in combination with otheradditives such as metal deactivators, antiknock compounds, antirusts andthe like. The inhibitors can be added to the gasoline with or withoutuse of an auxiliary solvent, solutions in aliphatic alcohols such asisopropyl alcohol being preferred. In the case of the compositionscontaining N-n-butyl-N- isobutyl-p-aminophenol, isobutyl alcohol admixedwith isopropyl alcohol is the preferred solvent both from the standpointof gasoline solubility and solubility in the solvent. Solutionscontaining from about 50% to about 55% of the inhibitor blend in thesolvent are preferred.

The reasons for the synergism between the monoalkylated and dialkylatedinhibitors is not understood, and the invention is not limited thereby.Although the invention has been described in detail with reference topreferred embodiments thereof, variations and modifications can beeflfected within the spirit and scope of the invention as describedhereinabove and as defined in the appended claims.

I claim:

1. Gasoline containing cracked stock having incorporated therein astabilizing amount in the range of 0.001% to 1% by weight of asynergistic inhibitor composition consisting of a mixture of 190% byweight of N-n-butyl- N-isobutyl-p-aminophenol and 99-10% by weight of N-n-butyl-p-aminophenol, said composition including about by weight ofN,N'-di-n-butyl-p-phenylene diamine based on the weight of saidN-n-butyl-p-aminophenol.

2. Gasoline containing cracked stock stabilized with 0.001% to 1% byweight of a synergistic inhibitor mixture of 2 5-35% by weight ofN-n-butyl-N-isobutyl-paminophenol and 75-65% by weight ofN-n-butyl-paminophenol, both based on the weight of said mixture.

3. Gasoline containing cracked stock having incorporated therein astabilizing amount in the range of 0.005% to 0.05 by weight of aninhibitor composition of a mixture of 25-35% by weight ofN-n-butyl-N-isobutylp-arninophenol and 75-65% by weight ofN-n-butyl-paminophenol, both based on the weight of said mixture, saidcomposition including about 10% by weight of N,N- di-n-butyl-p-phenylenediamine based on the weight of N-n-butyl-p-aminophenol.

4. Gasoline containing cracked stock stabilized with 0.001%"to 1% byweight of-a synergistic inhibitor mixture of 1-90% by weight ofN-n-butyl-N-isobutyl-paminophenol and 99-10% by weight ofN-n-butyl-paminophenol, both based on the weight of said mixture.

5. Gasoline containing cracked stock stabilized with 0.001% to 1% byweight of a synergistic inhibitor composition consisting of 90-100% byweight of a mixture of 1-90% by Weight of N-n-butyl-N-isobutyl-paminophenol and 99-10% by weight of N-n-butyl-p-aminophenol, and 10-0%by weight of N,N'-di-n-butyl-p-phenylene diamine.

6. A composition capable of synergistic inhibitor activity whenincorporated in gasoline containing cracked stock, said compositionbeing a mixture of 1-90% by weight of N-nbutyl-Nisobutyl-p-aminophenoland 99- 10% by weight of N-n-butyl-p-aminophenol.

7. A composition capable of synergistic inhibitor activity whenincorporated in gasoline containing cracked stock, said compositionbeing a mixture of 1-90% by weight of N-n-butyl-N-isobutyl-p aminophenoland 99- 10% by weight of N-n-butyl-p-aminophenol, said compositionincluding about 10% by weight of N,N'-di-n-butylp-phenylene diaminebased on the weight of said N-nbutyl-p-aminophenol.

8. A composition capable of synergistic inhibitor activity whenincorporated in gasoline containing cracked stock, said compositionbeing a mixture of 25-35% by weight ofN-n-butyl-N-isobutyl-p-aminophenol and 65 by weight ofN-n-butyl-paminophenol.

9. A composition capable of synergistic inhibitor activity whenincorporated in gasoline containing cracked stock, said compositionconsisting of about 10% by Weight of a mixture of 2535% by weight ofN-n-butyl-N-isobutyl-p-aminophenol and 75-65 by weight of N-n-butyl-paminophenol, and about 10% by weight of N,N'-di-nbutyl-p-phenylenediamine based on the weight of said N-n-butyl-p-aminophenol.

10. A composition capable of synergistic inhibitor activity whenincorporated in gasoline containing cracked stock, said compositionconsisting of 100% by weight of a mixture of 1-90% by weight ofN-n-butyl-N-isobutyl-p-aminophenol and 99-10,% by weight ofN-nbutyl-p-aminophenol, and 10-0% by Weight of N,N-din-butyl-p-phenylene diamine based on the weight of saidN-n-butyl-p-aminophenol.

References Cited in the file of this patent UNITED STATES PATENTS2,081,130 Atwell May 25, 1937 2,163,640 Von Bramer et al June 27, 19392,250,501 Rosenwald et a1 July 29, 1941 2,275,311 Pederson et a1. Mar.3, 1942

1. GASOLINE CONTAINING CRACKED STOCK HAVING INCORPORATED THEREIN ASTABILIZING AMOUNT IN THE RANGE OF 0.001% TO 1% BY WEIGHT OF ASYNERGISTIC INHIBITOR COMPOSITION CONSISTING OF A MIXTURE OF 1-90% BYWEIGHT OF N-N-BUTYLN-ISOBUTYL-P-AMINOPHENOL AND 99-10% BY WEIGHT OFNN-BUTYL-P-AMINAPHENOL, SAID COMPOSITION INCLUDING ABOUT 10% BY WEIGHTOF N8N''-DI-N-BUTYL-P-PHENYLENE DIAMINE BASED ON THE WEIGHT OF SAIDN-N-BUTYL-P-PHENOL.